`.canSetCaretBefore`: Fixed critical bug.
`.nodeAfterSel`: Simplified!
`.setCaretBefore`: Restricted to text nodes and certain `br` elements.
`.canSetCaretAtStartOf`: If one browser can't do it - none can.
`.setCaretIn`: Semantic fixes.
Selection API docs: Some clarification regarding selection API.
Using `WYMeditor.NODE.TEXT` instead of `3` in some places.
Code comment typo.
'Selection Setting and Getting' documentation fixes.
Merge branch 'master' into selection_api_bug
Merge pull request #523 from mightyiam/selection_api_bug

Selection API fixes